Thunder's Half
by Nightsmoke
Summary: In which Odin screws up royally, the Casket of Ancient Winters is stolen, and something is the matter with Thor. Gift fic for the fantastic Helennotoftroy, multi-part.
1. I

All characters © Marvel Comics

_Summary: _In which Odin screws up royally, the Casket of Ancient Winters is stolen, and something is the matter with Thor. Set post-Avengers, before Surtr uses the Casket in the Marvel-verse.

**Note:** This is a gift-fic for the amazing writer Helennotoftroy. Get well soon!

* * *

_**Thunder's Half**_

**I.**

"There is a catch," Odin said, looking at Gungnir thoughtfully.

Loki, already knowing this, veiled his inner rancor with something resembling a smile. "Naturally," he said. As if aiding the pathetic Midgardians in exchange for his freedom was not appalling enough. He knew what the Allfather was going to say; it did not help that Odin's good eye crinkled with a look that was genuinely apologetic. It made Loki's stomach curl over itself and bubble.

"The alteration bindings are over a thousand years old and are rightfully troublesome to break," Odin admitted, still eyeing his spear, "but I shall do so in hopes that you will return to me."

"Of course, so that I may be imprisoned in Urd's well once more, "Loki sneered, all attempts at a smile dissolving. "Tell me you are not planning to undo the spells of Mimir all in name of a single dwarf's frivolities? Really, father," his eyes narrowed, "you must be losing competence with your old age."

Odin finally tore his gaze away from Gungnir and peered at Loki from the dais. "If you had not destroyed our guardian armor Vidar would have never been capable of stealing the Casket in the first place." His brow was furrowed, skin folding over itself thunderously behind his shock of grizzled white hair.

Loki's sneer deepened at the Old Norse word for guardian armor. He much preferred the Midgardian moniker _Destroyer._

"Is your beloved Thor so ill-equipped on Midgard that you call upon my, shall we say, _latent physicality_ in lieu of the Avengers' efforts?" he asked. As if he had not been humiliated enough already.

Ignoring Loki's mordant, unblinking stare Odin replied, "Your true heritage is what makes you so apt for this task. As ironic as it sounds," he went on, gaze decidedly abstruse, "there is not a single warrior save for you to whom I would entrust the safety of Midgard. You are getting a second chance, my son."

After a minute of rubbing the scars around his lips and chin in a bitter burlesque of contemplation, Loki opened his palms, conceding. "Do not think you hold leverage over me, father. It is only because I detest the bowels of Yggdrasil so that I am accepting your offer," he said.

Odin's mouth tightened around the edges. "Loki," he began.

"You assume I enjoy being forced into a thousand-year slumber at the bottom of a well? I will do your bidding—not as your son," Loki said, overriding Odin, "but as your Jötun slave. I will fain retrieve the Casket of Ancient Winters in return for my exculpation and shall refrain from using it for, ah, further attempts at genocide." He picked at a spot of nonexistent lint on his robes and raised his eyebrows. "If you doubt my truths take a look for yourself from your little silver walls of Hliðskjálf."

"I do not understand it," Odin said, shaking his head sadly. "When did you become so bitter, my son?"

"Since a man found me and raised me as a bastard," Loki replied. "You should have left me to die, _Allfather._ I rather think I would have preferred it."

He knew his words had the desired impact and his stomach did another flip before balling into a tight knot because Odin actually looked guilty, the wretch. The lost boy in Loki almost protested. For all of the deception, Odin had still been a father figure. Loki quickly pushed that thought away, filling its void with an image of King Laufey baring his yellow teeth and breathing icicles into the snow.

"Loki. Perhaps your anger will fade and your heart will soften with time, but for now I banish you to Midgard," Odin said, quietly, final. He lifted Gungnir and abruptly, his voice rose. "White to black, blue to midnight. I now lift these curses from you—"he uttered a word of power in Allspeak—"and summon the enchantments of Freya to bring you to your destination."

Loki suddenly felt very cold. The sensation began in his chest and spread, like a spill of liquid milk, to his fingers and toes. He felt himself _shifting;_ every molecule stretching and fading with the pull of magicks past.

"Do your duty and return to me, my son," Odin concluded, as Loki shimmered and vanished in a puff of light. He lowered his spear and he bowed his head in the silence that followed Loki's departure. He remained like that for some time.

"And forgive me."

x

With the Bifröst still in repairs, Asgardian ventures to other realms were temporarily limited. This certainly did not hinder the Warriors Three, who opted for stone-circle travel, as well as other Æsir vigilante who chose less desirable methods of transportation.

Loki vaguely recalled, some eons ago, having questioned Thor about the dark energy Odin had used to summon him in the absence of the Bifröst. Now, as he was dematerialized and scattered across the realms, Loki realized something terrible.

Odin's spells of travel (a product of Vanir's lost scrolls) undoubtedly consisted of dark energy. As a practicing sorcerer and agent of the ancient Seid of Freya, Loki descried this in a manner of seconds. He also recognized that the energy was all-corrupting. There were threads of Karnilla's black matter woven in, not to mention tendrils of Draugr, red snaps of revenge from Bergelmir, and traces of ash from Surtr himself. It would have terrified a lesser sorcerer down to the soles of his boots.

Dark energy in and of itself was only remotely problematic; if one did not know how to dispel its deleterious effects and let himself be corrupted by it, however, it could have unpleasant results. Loki gathered his own magic within the corners of his consciousness and dispelled the dark energy before it could start eating away at his essence. He was left clean, white, but with a sense of disquiet gnawing at his mind in the place of magic.

Was this what the Allfather had been using all this time to send Thor to Midgard?

Chances that Odin knew his spell was corrupt, or of its prolonged influence on those who were subject to it on occasion, were slim. If Loki were fully materialized he would have groaned as he realized what this meant. Thor. Of course.

Thor was not the imbecile Loki often made him out to be, but he was about as well-versed in spells as a battleswine. He would have had no idea that the magic used to transport him to Midgard was also slowly polluting him from the inside out. A double-headed snake, if there ever was one.

Had Tony Stark known of this, he would have sympathized.

x

Tony Stark, at present, was sneezing into the inside of his mask—an experience that shall not be recounted in order to preserve the well-being of everybody around. He subsequently let out a string of curses that made Steve glance over.

"You alright, Stark?"

"Peachy," Tony replied, sniffing. "I love my interface covered with mucus. Shouldn't there be a law, or something, against Scandinavia being this cold?"

"You should see the mountain peaks of Jötunheim," Thor said. "Goats there are known to freeze solid in the middle of the night."

"Thanks for the lovely image," Clint said as he rubbed his fingerless gloves together. "By the way, I like the getup." He gestured to Thor's armor, which was slightly different from what he had worn in New York. It was missing the six circular discs down the torso and the cape was a few shades darker, among other minor alterations, yet the garments still projected a sense of authority and power.

"My raiment is most suitable for the forests of Kiruna," Thor explained, gesturing around them. "We will need all reinforcements possible if we are to kill Vidar the dwarf."

"We're not killing him, just taking him down," Steve reminded him. Thor frowned, as if puzzled that there was a difference between the two expressions.

"If Vidar opens the Casket of Ancient Winters—"

"The Earth will be in mortal peril, we know," Tony said. "It's not like it hasn't happened before. Just take this guy back to your place once we stop him, like you did with Loki—"a mechanical arm came up and made a dismissive gesture in the air—"and do with him what you will there. Capital punishment isn't really up our alley."

"I would have his intestines strung out and made into a wreath," Thor remarked casually—almost as casually as he had described the goats of Jötunheim. Tony dropped his end of the end of the conversation then, deciding that whether serious or not, Thor's comment did not merit a response.

"All right, boys," Natasha said, catching up with them and sliding the last of her weapons into place on her belt, "are we ready to defrost?" Nobody noticed Steve's Adam's apple bob once in a swallow.

Clint paused a moment as the others passed him, his eyes still resting on Thor. His soldier's sense, which he had come to regard as an actual sense despite the cliché, was throwing off sparks. Something was off, but damned if Clint knew what it was.

It was not the looming battle but this lack of insight that bothered him most of all.

_to be continued._


	2. II

All characters © Marvel Comics

_Summary: _In which Odin screws up royally, the Casket of Ancient Winters is stolen, and something is the matter with Thor. Set post-Avengers, before Surtr uses the Casket in the Marvel-verse.

**Note:** This is a gift-fic for the amazing writer Helennotoftroy. Get well soon!

* * *

_**Thunder's Half**_

**II.**

The moose was a true beauty. The fully grown bull was a giant, even for its species—well over two meters tall, fur shining a dark mahogany, antlers sharp and bone-white. It snorted hot breath into the winter air, head poised.

Loki wanted to pounce on it and eat it raw.

As if picking up on this thought the moose flicked its stub of a tail and lumbered off into the trees with a final snort.

Loki grimaced, disgusted. Never before had he craved such a thing; the Æsir generally considered raw meat uncouth and ill-fitting for the opulence of Odin's feasting hall. But now Loki realized, as he raised a blue, exposed arm before him, he was no longer Æsir. At least the Allfather had managed to undo _that _spell correctly.

It was Mörsugur in Midgard, the very nadir of winter. January, as they now called it. Snow speckled the evergreen populace like unbaked flour and the air was steely and crisp. Hardly fortuitous weather for the weak Midgardians, but pleasantly comfortable for Loki. The icy gusts merely tickled him and swirled his hair—now a little bit longer—around his face and neck.

Loki walked through the snow, sniffing the air experimentally. The raucous little dwarf was close. Judging by the faint sound of crashes, carried to him by the wind, and the flocks of birds taking off in the distance, Vidar had undoubtedly opened the Casket. Loki sniffed again, picking up the scent of smoke, metal, sweat. The dysfunctional heroes, no doubt. He crinkled his nose.

Thor was with them, and this made Loki pause for a moment, drawing his lips together. He even _smelled_ wrong.

A raven perched on the branch of a nearby tree squawked once.

Loki looked up, unsurprised. "Greetings, Huginn," he said. "You need not keep watch." The raven cocked its head, blinked its fishbowl-black eyes and squawked again, more subdued.

Loki smirked. "I always keep my word."

There was a frozen lake at the foot of the trees, and Loki approached it cautiously. He knew that as a Jötun his bone density was greater and would shatter the ice no matter how thick the ice appeared.

The ice itself was another work of beauty in this realm, for instead of the bumpy, crusty layers that generally formed from moving water the ice covering the lake was smooth and reflective. Out of curiosity, Loki leaned over and peered into the lake.

He already knew what he looked like; he had seen Jötuns up close as he had put a sword through their hearts.

Slowly, almost delicately, Loki traced the runic impressions running down his arms and over his face and chest. They reminded him of sand dunes under a fresh moon. The color of his skin enhanced the white of his canines, which were slightly pointed, and the wet red irises. The minute scars around his lips and chin from the muzzle were a light, faded blue.

Another crash sounded in the distance and a breeze blew from the west. Loki rose. He could defeat Vidar, as he was now, despite how repulsive he looked. Everything was stronger—his senses, his power, his magic.

The thought came to him of simply taking the Casket and absconding to somewhere outside the Nine Realms, someplace where Heimdall could not bear his gold teeth at him. He could do it too. What was keeping him?

Huginn ruffled its feathers uneasily. "Relax," Loki told the raven. He would not flee, and he knew exactly what was grounding him. Rather, who. The idiot.

Loki had seen what an ill-minded Thor could do to a dining hall, let alone a landscape and a population. Odin would surely be heartbroken at the figurative loss of another son. But it was not the destruction that made Loki grit his teeth against turmoil. A normal Thor was naïve, yet bright and ingenious when he had to be. He pleaded again and again _ad nauseam_ for his brother's reconciliation, which accounted for both his best and his worst qualities. Loki played hard to get, and he liked it that way.

He had seen (and perhaps experienced firsthand) how darkness could change a person. A darker Thor—a Thor corrupted by magic—would not do any of the things aforementioned, which could be relieving on some level. No more mawkish pining. No more whales' grins or mead-guzzling contests or jibes at his helmet. Asgard would lose the throne, Mjölnir would destroy the land, and Thor would finally cease his attempts to reconcile with Loki.

Loki would never admit aloud that he'd miss them.

Huginn gave another scratchy caw as something exploded a few miles away. "I am going," Loki snapped at the bird, scowling. He spared himself another glance at his reflection on the ice and froze mid-turn. There was something there that had not caught his eye before.

Two nubs, on either side of his temples, just below the hairline. Small yet, but they would grow with time. They poked through the skin and were perhaps made of ivory. Horns. _Horns,_ for Valhalla's sake.

Something about this realization suddenly brought it all home for Loki. With an inarticulate scream he brought his fist down upon the ice and shattered it. The surface of the lake splintered with a sound like grinding bones and the glassy reflection broke into slivers of ice. Sheets of ice separated and the water beneath undulated violently.

Breathing hard, Loki watched as the lake settled back down and some of the ice drifted away. The heavier chunks sunk to the bottom. After straightening up and dusting off his front, he began to walk again.

x

Natasha Romanoff was smacked, almost literally out of her boots, by a mass of semi-hardened snow. She did a pinwheel in the air and landed awkwardly on her elbows some feet away from Thor. Thor seemed too preoccupied with deflecting a spear of ice to ask if she was unharmed.

Most of the forest around them was in splinters and chips. The Avengers had fortunately directed the battle to a slightly less-populated area, but the Casket of Ancient Winters was a force of pure destruction. It razed anything and everything in its path, turning the atmosphere into a snowy graveyard and frozen bones.

Without the Destroyer to properly guard the Casket, several otherworldly beings had attempted to steal it (only one to this day successful) since the New Mexico Incident. Apparently, it was the hot new item to have in the Nine Realms. The perpetrating dwarf, currently seated on a dune of ice roughly the height of a tall building, cackled gleefully and sent another wave of blizzard from the Casket down on the Avengers.

"You know," Tony began, using his heat guns to combat some of the blast, "I'm not really much of an environmentalist but destroying that many trees _can't_ be good for the forest."

"Your enterprise makes clean air, of course you're an environmentalist," Steve said from behind his shield. He had a long scratch down one cheek (courtesy of an icicle fusillade) and the sweat on his brow had frozen into hard little beads. He was panting, nowhere near one hundred percent but giving earnest attempts to appear that he was.

"Aren't we irritable today? Well, since you put it that way—"Tony was cut off by an abrupt shove from the Hulk, and not a minute too soon; an ice boulder the size of a horse landed right where he had been standing a second ago.

"Thanks, big guy," he said, before firing another fire blast at the dwarf.

"How's the plan of attack coming?" Clint asked Thor over the wind and noise of battle. Some time ago they had formulated a strategy of steady advance until they—theoretically—had the Casket surrounded. At the moment the plan was not going as swimmingly as the team had anticipated. Their diversions did little to actually distract, and the Casket was proving to be just as difficult as Thor had described it to be.

Atop his ice fortress, the dwarf chittered something and did a little dance that looked like some bizarre shuck-and-jive. Steve could not catch what had been said, but Thor stiffened and began to swing Mjölnir faster at his side.

"We need Banner on the offensive," Thor shouted back to the team. "Vidar means to open the Casket further!"

Great, just what they needed. Steve sighed and braced himself, closing his eyes for a brief moment in hopes that his heartbeat would settle. He felt a poke in his side and whipped his head around.

"Whoa there, Cap." It was just Tony. "You've been a little jumpy today. Did Thor give you his coffee again?" he asked Steve. Steve almost answered honestly, but there was something about talking to Stark with the mask on that still felt alien, uncomfortable.

"Don't worry about me," Steve replied, straightening up. "Let's just get this King off his Hill."

"Hey, pop culture bonus right there," Clint said from his left in the midst of shooting arrows. The eyes of Stark's mask lingered on Steve for a moment longer. He—

A pile of rapidly flying snow hurled toward them. Steve raised his shield and Tony successively got knocked twenty feet into the air by a hidden block of ice that had sprouted from the ground. Similar jets of frozen water exploded from between the trees, causing the Avengers to dodge every which way. The attacks from the Casket were getting stronger.

"Are you sure the big guy can take it?" Tony asked Thor once he had leveled himself in the air. "I mean, that ice is—"

"Have I not informed you of the Casket's power already? Do as I say and maybe you will live to see another sun," Thor snapped as a jet of ice encased his leg up to the knee. He pounded a closed fist against the ice to crack it and free his leg.

"Sheesh, we're all a bit tetchy today," Tony muttered, before flying away to get Banner.

Steve, on the other hand, had directed all his focus to Thor's leg, which was still frozen in a block of ice. He could not seem to look away.

_(put her in the water)_

_Breathe,_ he told himself as his airways suddenly felt as small as a pinhole. Other missions had not posed a problem like this. Then again, the other missions had not posed the threat of being refrozen. Perhaps he was not as "over" the whole cryogenics thing as he had presumed.

_Run,_ his instinct screamed, silent to everybody but him. His chest felt tight, painful; almost as if he was asthmatic again. Fresh sweat popped up along the skin of his temples. Steve was no stranger to fear. Fear was a psychological hindrance, familiar to the soldier. This, however, felt more like panic.

_Forget them and run. You'll be frozen again._

Steve's shield trembled in his grip. He could never run. It was just a little ice, right? He would simply have to man up and deal. Fight with your body, not against it, he reminded himself. Courage.

And so he did, until the largest cyclone of ice and snow of them all spurted from the ground like a geyser with deadly accuracy and hurled Steve half a mile away.

_to be continued._


	3. III

All characters © Marvel Comics

_Summary: _In which Odin screws up royally, the Casket of Ancient Winters is stolen, and something is the matter with Thor. Set post-Avengers, before Surtr uses the Casket in the Marvel-verse.

**Note:** This is a gift-fic for the amazing writer Helennotoftroy. Get well soon!

* * *

_**Thunder's Half**_

**III.**

In the time it had taken him to walk three miles, Loki had devised twenty-nine elaborate battle strategies step by step. Only ten of these actually consisted of retrieving the Casket of Ancient Winters; the rest were, infuriatingly, fixated on the problem of Thor.

He was busy setting the groundwork for his thirtieth plan when he caught a splash of blue from over the hill ahead of him. In all fairness, Captain Rogers was considerably more surprised to see Loki than Loki was to see him.

Rogers, to put it mildly, gawked. "Loki," he said. It almost came out as a question. He instinctively reached for his belt, but Loki held his palms up to indicate that he meant no immediate harm. Loki could see the thoughts flitting across Rogers's features like brightly colored flags: recognition, confusion, hostility, suspicion, awe. The last was definitely awe, however faint. It was gone almost as soon as it had appeared, but for the life of him Loki could not understand why Rogers would have that expression on his face.

"Why hello, Captain," he said, smooth as moose fur. "Not joining the battle today?"

Rogers actually looked guilty. Loki's red eyes narrowed, drinking in the new expression and swirling it in his mouth, trying to discern its taste. The captain had clearly been separated from the team, but as their leader he should have been bursting at the seams to return to them. Instead, he was sitting on a rock in the snow. How odd.

"Why are you here, Loki?" Rogers asked in lieu of a direct answer. His eyes ran over Loki's blue skin, giving him another once-over. _And why do you look like that?_ was the unspoken question, but Loki heard it as if it had been blasted through Gjallarhorn.

He gave a one-shouldered shrug. "The same reasons as you," he answered. "I will benefit from returning the Casket of Ancient Winters to Asgard, so you can interpret my aid today as a temporary truce of the sorts. I do not offer perfidy but a genuine alliance in the name of a greater cause."

"Which is?" Rogers asked. Loki only responded with a wry smile.

"Enemies are known to join forces from time to time," he responded. "Allow me to offer my assistance, Captain Rogers, despite our unconscionable and slightly un-agreeable history." Loki smirked and watched Rogers mull it over. His skin may have turned blue but his tongue was still silver.

After a minute Rogers dipped his head in agreement. He sighed, looked into the distance, and finally rested eyes on Loki. "Thor didn't say you were coming."

"No, I do not suppose he did," Loki said. He gestured to the sky. "Shall we, Captain?" Rogers was still sitting in the snow, propped on a rock and twirling a broken earpiece around in his fingers. He looked…hesitant, which, giving what Loki knew about him (he had seen the good Captain jump out of a plane bareback in a storm), seemed decidedly out of place.

"Something the matter?"

Rogers gave him a dark look. "Let's go," he said, jumping up and wiping some crusted blood from his cheek. His eyes fell to the footprints in the snow behind Loki. "You walked?" he asked. A loud crack filled the air and a grubby plume of smoke drifted up from the tops of the trees in the distance.

Loki tilted his head toward the sound and smiled faintly. "What can I say?" he replied. "I like the quiet. But you are avoiding the question, Captain." Oh, how fun it was to be able to tease somebody again! The rest of the journey would be most enjoyable.

"Yeah?" Rogers began to walk. "I'll answer that if you tell me why you are, uh, _colored."_

"Since you put it so nicely," Loki said, rolling his eyes, "this is my true form." Rogers raised his eyebrows.

"I am of Asgard but not Æsir. A foster child, you might say. The Allfather thought this form would be more appropriate to deal with your world's current problem."

"You don't sound too happy about it," Rogers noted. He sniffed, nose pink from the winter air. "Does this mean you and Thor are not actually brothers?"

_Of course it does, you dolt._ "That is all you shall hear from me, unfortunately," Loki said, shaking his head in mock pity. "I'm rather more curious about you, Captain."

Rogers's nostrils flared and he tightened his lips begrudgingly. "Fair enough," he said. "When you're cryogenically frozen for a few decades you tend not to look at ice the same way."

"Ah," Loki nodded, "so you ran."

Rogers glared. "I did not run. I got hit."

Loki had been looking at the snow around his boots, but at this he turned and met Rogers squarely in the eye. "Oh please. There is no difference," he said. "Fear governs your subconscious. It is human primitiveness at an extremely base level, after all." Rogers gave him a quizzical, if slightly offended look.

"Perhaps you wanted to get hit so you could be away from it," Loki continued. He smirked, unable to help himself. "How cowardly."

"Any of the others would have killed you by now," Rogers said, holding up a finger. "Be thankful that I can tolerate you on an extremely base level."

Loki blinked. Who would have guessed that Rogers had a tongue on him as well? "Well that's a start," he said, not surprised to find that he had broken into a grin.

x

The Hulk did not take kindly to having an icicle the size of a telephone pole spearing through his deltoid. To top it off, he was in his boxers and the outside temperature was negative ten degrees Fahrenheit. Even he felt some of the cold.

A second spear pierced his upper thigh while another one went straight through his forearm. The Hulk roared, and some of the thinner ice coating the ground cracked.

Tony had prepared for "icing problems" in advance, but the unrelenting power of the Casket was still causing major damage to his suit. Clint was inhibited by a broken leg, Steve was MIA, and Natasha was getting tired. The only one still fully in the game was Thor.

"Watch it!" Tony shouted as Mjölnir whizzed by within an inch of his helmet. The hammer subsequently splintered an entire evergreen tree that had been frozen in a block of ice. For a minute it seemed that it was raining crystals, which would have been transcendent had it not been for the imminent danger of a falling tree. Tony quickly moved the trunk out of the way as it began to fall.

As Thor became more involved in the battle he grew increasingly less mindful of his surroundings. Tony had always known Thor to be calculating in battle, strategic. He was like a natural disaster incarnate (much like his brother, Tony thought dryly), but he was always careful to direct his destructive proclivities away from civilians and the team. Tony could tell that Barton and even the Hulk, to some extent, had picked up on the change. First Rogers, now Thor.

"Stark!"

As if sensing his thought, Barton gestured to the Hulk. His leg was twisted spectacularly beneath him and his face was wan and pinched with the pain. He was still shooting what remained in his arrow reserves, but even he could see that his efforts were ineffective.

The dwarf had pinned the Hulk against an enormous spruce and was holding the Casket directly in front of the Hulk's chest. Tony flashed Barton the okay and whizzed over.

"Oh no you don't," he said, and could almost feel JARVIS channeling the exact same sentiments.

x

"Now fire I have a strong disliking to," Loki mused aloud, simply to make their short journey as annoying for the good captain as possible. He also enjoyed the company and banter of somebody who was not actively trying to kill him, more so than he would care to admit.

It had been so long, because of the Well.

There was just something so delightful about having a simple conversation with someone that Loki took far too much pleasure in. Everyone on Asgard harbored the idea of Talking Bad, Fighting Good, but no one saw the true gems that could be found in just words and expressions. You could uncover an enemy's fears and secrets; even his entire life's reflections if you rubbed verbal elbows hard enough to create a shine.

Prying people open with discussion had become an almost compulsive habit of Loki's, much to the chagrin of those around him.

"I thought I said I didn't want to talk about it," Steve grit out. There was a hole in one of his boots and the snow was seeping in, uncomfortably soaking his sock and freezing his toes. "I don't make you talk about your—"he waved his hand at Loki's blue skin—"what do I even call this?"

"Jötun," Loki replied, because it was more difficult to poke fun at than _frost giant._ "I am Jötun royalty, which is actually a lot harder to talk about than one might think. It makes me want to dig my fingernails into every eye socket of the House of Odin and tear out their brain stems in little ropes. But you do not see me complaining, Captain."

Rogers looked mildly disgusted for a minute. Then he seemed to recall who he was talking to and shook it off. "Look," he said, "anything to shut you up until we get to the Casket. We've all got issues, like you said. Freak shows." Loki's grin widened, and Rogers tried not to notice the acrimony behind it.

"Trauma, shock, call it what you will. I don't suppose you'd understand what it's like to be in suspended animation for decades." Rogers grimaced. "A real gas. Asleep in water while the world passes you by."

"Actually," Loki pointed out, "you'll find that I do."

Rogers turned toward him. "What?"

_to be continued._


	4. IV

All characters © Marvel Comics

_Summary: _In which Odin screws up royally, the Casket of Ancient Winters is stolen, and something is the matter with Thor. Set post-Avengers, before Surtr uses the Casket in the Marvel-verse.

**Note:** This is a gift-fic for the amazing writer Helennotoftroy. Get well soon!

* * *

_**Thunder's Half**_

**IV.**

Clint Barton could not decide what he should be more confused about. Presently, there was the fact that they had all had their asses handed to them by a box that looked like it belonged in a pack rat's garage sale. Thor was acting oddly. Rogers had been blasted somewhere into a snowdrift and had somehow broken his communicator in the process. Sure, Rogers was a pro at being MIA, but he never did it on _purpose._

Then there was the fact that Loki was here. The guy who had leveled downtown Manhattan simply because he had a brother complex; the guy who had casually strolled in through the trees with _Rogers_ at his side, of all people; the guy who was at present blue as an ever-loving smurf and who was fighting in their defense. Clint did not think that _anyone_ had seen that coming.

So yeah, there were several things Clint could be confused about. He decided to close his mouth so he bore less of a resemblance to a beached fish and to save the questions until later. As he was no longer able to fight he had gotten creative and had taken two slabs of nearby bark to use as a splint for his broken leg, tying them together with the cloth from his parka (the thing had been shredded beyond normal use anyway).

Clint could see similar expressions of bewilderment on Natasha and Stark's faces. Even the Hulk had forgotten that he was supposed to be angry as they watched Loki battle the snow and ice seemingly with ease. The dwarf, becoming enraged, started increasing his attacks. The Casket glowed blue and the air grew colder. Steve quickly ushered the Hulk away from the battle while Stark similarly used the last of his power reserves to fly Clint and Nat to higher ground, where they could watch Loki kick up the figurative dust from a safer place.

And kick up the dust Loki did. Clint's eyes, as good as they were, could not precisely keep up. There were spells, clones, magic; it was all a blur and in less than twenty minutes Loki had sealed the Casket shut with the dwarf tightly bound at its side. In the midst of all the action even Stark had lost the ability to offer any sort of quip or witty riposte (only a temporary affliction, Clint was sure).

Thor watched all of this with an expression that was disconcertingly unreadable. He squeezed Mjölnir at his side while his eyes followed his brother's movements. His mouth was pursed in an abstruse, thin line. Not a word escaped him.

When it was all said and done Loki raised one foot and brought it down on top of the Casket in the universal gesture for conquer and triumph. "I believe this solves your problem, does it not?" he asked to the deafening silence that greeted him.

Loki raised an eyebrow when no one said a word. "Please," he nodded to the wreckage around them, "if I am to rule this world one day I'll not have it looking like this. You all should be thanking me."

"Brother," Thor finally managed, looking grave yet conflicted despite himself. As if his words were a spoken cue, the Hulk growled and Natasha and Stark both reached for their respective weapons.

"Anyone want to tell us why Brainy Smurf is here?" Tony asked, his firearms still poised. He looked at Thor.

"If he takes the Casket back to Asgard Odin will set him free," Steve said—almost recited, like a student would in class. Clearly he did not relish the idea.

Neither did Clint. "I don't like the sound of that," he muttered. He fingered the last of his arrows, ignoring the splinters of screaming pain in his broken leg with considerable effort. The pain could actually be useful here, Clint thought dimly. Out of everyone on the team no one harbored contempt against Loki like he did. Perhaps the pain would prevent him from doing anything that he would regret later.

"As I already explained to Captain Rogers, I am here to help today," Loki said. "Besides. The real problem is still at hand."

Clint scowled. "You mean the problem of what to do with you?"

"Hardly," Loki replied, leering. With his red eyes and nubs of horns he looked positively demonic. Clint felt sick.

"It has been a while has it not, Agent Barton? I do so miss your services." Loki paused as all the remaining color left Barton's face. "Humor me this once, Agent. If you were to observe my brother's garments, what could you tell me about them?"

The question took Clint completely by surprise and he blinked, trying to discern the meaning of an apparent non sequitur. Perhaps the pain had gotten to him after all. "His clothes?" he managed.

Thor was silent. Tony readied one of the smaller capsules on his suit's armor. "Does it matter?" he asked.

"Oh, I believe it matters a great deal." If Tony had not known any better he would have said that Loki actually sounded impatient. "Come now, Barton. What do you see?"

Clint's scowl deepened. Reticence was severely tempting; he was bleeding from various places, cold, and his leg looked like a Reed Richards workout gone wrong. He told himself that he should not feel compelled to answer to Loki ever again.

But the feeling that something here was wrong, coalescing with Clint's natural perspicacity, won him over in the end. He was an observer—a watcher, forever born and bred, and the opportunity to pick apart things with his eyes—the _desire_—was just too strong to resist. So, he scooted a few feet back and looked up at Thor, tilting his head.

"The breastplate doesn't have those circular discs that it had last time," Clint began. "And he doesn't have the, uh, I think you'd call it a…rerebrace? You know, the metal on his arms in the crisscross pattern. I don't see why this matters much. He probably just changed for the weather."

Loki did not bother to point out that the Æsir were extremely tolerant of Midgardian winters. "Go on," he said.

Clint shook his head. "Other than that, the only other thing I can see is that he got a new cape," he said. "The old one was a brighter red than this."

Loki showed more teeth. "Impressive," he said.

"Are we done talking fashion?" Natasha asked, crossing her arms and looking at Loki pointedly.

"Far from it, Agent Romanoff," Loki answered. "Your precious Agent Barton managed to point out every detail to aid the fact that my brother is not who you think he is."

"Because he changed his clothes?" Tony snorted. He had raised his face plate and was squinting at Thor as if Thor was likely to spontaneously combust at any minute.

"Cease this nonsense, brother," Thor said quietly.

"Did you know," Loki said, overriding him, "that on Asgard your armor represents your title?"

"Loki, I am warning you."

"For the _righteous_ son of Odin—"Loki practically hissed the word—"the scales on his left arm represent Buri. The ones on the right represent Bor. The discs on the breastplate also depict the line of blood. As for the cape, well, belief goes that the more resplendent the color the stronger your sense of purpose and connection to Yggdrasil is.

"Now, what do you suppose it means when your rerebraces are missing and your cape is faded?" Loki paused, taking in their expressions. Rogers looked like someone had just told him that two plus two had always equaled seven, whereas Romanoff and Stark were attempting to reach some vague understanding. The Hulk grunted once and visibly began to shrink. Stark, momentarily distracted by the transformation, went to fetch some clothes for Banner and explain the situation to him.

Thor looked frustrated, as if he did not fully understand himself. To his credit, he probably didn't.

Tony thought back to May, during the Chitauri incident. He recalled that Thor had been in full getup once they had reached the streets of New York, but not when he had first arrived on the Helicarrier. Interesting, but all without meaning. Unless—

"When one is corrupted by magic or evil intent he loses his title," Loki answered for them.

Barton started to echo "evil intent" at the same time Rogers asked, "Then, uh, how come he can lift Mjölnir?" God, the English pronunciation was appalling. But Rogers had a point.

"I did not say that my brother's title is lost," Loki continued, "merely scrambled. The dark energy our father is employing to transport him to your realm is slowly taking over. If Thor makes any more trips here he really will be corrupted. A bag of cats, like me." He grinned, but it was a humorless grin. "A darker Thor could easily rip this realm apart."

"I wouldn't…" Thor began, but he looked unsure of himself.

"He already made Trolltunga," Loki said dryly.

Tony blinked a few times. "So the big guy's been a little grumpy, sure, but we all have our bad days," he pointed out. "He doesn't look particularly evil to me." But now, come to think of it, the Hulk had been rather edgy around Thor lately…

"Because he's not," Loki replied. "Not yet."

"Alright," Tony said, "a potentially evil Thor on our hands, and you; I don't know which one's worse. I don't even know if I believe you. But what are we going to do about it, and—"he turned toward Rogers—"what are we going to tell Fury?"

Loki held up a hand before Rogers could come up with something. "Allow me to deal with my brother," he said.

Thor started. "Loki, I must insist—"

"It is surprising that you have not commented on my new wardrobe, Thor. I believe this is your first time seeing it in all its, ah, _splendor."_ Clint did not think that Loki meant his clothes. As if to prove this point Loki absently ran his fingers over the runes on his bare arm, scrutinizing Thor.

Natasha stepped forward. "Do you have any proof that Thor is under an influence of some kind?" she asked.

"I have just explained everything to you," Loki said pointedly, a crease forming in his brow.

"Forgive us if we're not well-versed in magic," Steve said. "There's no way for us to tell if you're pulling one over on us or not. Prove what you just said and you might leave today in one piece." A flash of irritation crossed Loki's face, and Steve was pretty sure that the expression, for once, was genuine.

"You stupid, banal humans," Loki muttered, eyes narrowing. Banner, wrapped in a thermo blanket, tensed.

"Can I offer a proposal?" Natasha asked—calmly, because she sensed the atmosphere thickening. Loki raised an eyebrow.

"Thor," she said, "Jane is coming back from her retreat in the Rockies tomorrow, and she's been wanting to see you. How do you feel about that?"

Thor paused for a moment, then shrugged indifferently. "I suppose I will see her once I have attended to other matters." He nodded to the dwarf. "I shall like to deliver justice to this creature here, for one thing."

The first sprinklings of snow had begun to fall from the sky and they fluttered around the Avengers and Loki like bits of ripped paper. The Avengers were silent for a minute. Finally, after what felt like hours, Tony sheathed his firearms and gave Loki a flat look.

"He's all yours, Brainy Smurf."

"There is nothing wrong with me," Thor protested, eyeing Loki warily. His tone was menacing enough, but at the same time it lacked its undertones of authority. Loki took a step forward; Thor raised Mjölnir in warning and Loki stopped.

"Thor," he said, "allow me to help you." And for a minute he sounded all the inch the reasoning younger brother from the old days. Thor almost faltered. Almost.

"I do not need help," Thor snapped. "I know of your trickery and lies and I shall have none of it today."

Loki held up his hands. "I am not lying, not this time. All I am going to do is dispel the dark energy."

"And if I refuse your services?"

"Like the pig-headed brother I know so well?" Loki pursed his lips. "You know, even though it was you who broke the Bifröst father is going to blame _me_ for all of this."

Thor glowered. "Last I recall you did not give a damn about what father thinks." Behind him, Stark visibly winced.

Loki pulled in a deep breath. He held it for a few seconds and exhaled slowly, counting backwards from five. His breath did not create any steam in the air. "I guess we will have to settle this the hard way, will we not?" he said. With a nod to Vidar he added to the Avengers, "You should probably watch our little friend there." The dwarf gave a weak attempt against the bonds holding him down.

"Guys," Natasha said, touching a hand to her earpiece. "Fury wants us to pull out."

"Yeah, something tells me this won't be a normal sibling brawl," Bruce added. His teeth were chattering.

"What about Thor?" Clint grunted as Steve helped him up. Bruce took the Casket, holding it like he would fine porcelain.

"Leave him," Steve replied. The sky was darkening, and he did not think that it was all due to natural causes. Mjölnir crackled ominously at Thor's side. "Thor can get the Casket from us when he's…better, and he can return it to Asgard then. No offense Loki, but I don't trust it to you right now."

"No umbrage taken," Loki said mildly. "I shall agree to your terms." Thor raised his hammer above his head and Loki gave the others a somewhat exasperated look.

"It would be best if you leave now," he said. "We may change the landscape a little." He permitted himself a final smirk despite Mjölnir cutting a sizzling arc in the air above him.

"Until another day, mighty Avengers."

Tony lowered his face plate and simultaneously grabbed the unfortunate dwarf with one hand. Steve bit his lip, sparing Thor and Loki a final glance. Natasha touched his shoulder lightly and he shook his head. And so with the sounds of battle commencing behind them the team trudged away from the half-demolished forest to a more open space where the Helicarrier could pick them up.

Behind them, under the falling snow, a raven cawed once.

_to be continued._

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_**Author's note:** thank you to all who are reading this. I usually post my stories all at once, but decided to try putting it up in smaller pieces for a change. Unfortunately, I began this process before I actually began the editing one, so you may find little tweaks in previous chapters where I have put in some edits and cleaned things up. Enjoy!  
_


	5. V

All characters © Marvel Comics

_Summary: _In which Odin screws up royally, the Casket of Ancient Winters is stolen, and something is the matter with Thor. Set post-Avengers, before Surtr uses the Casket in the Marvel-verse.

**Note:** This is a gift-fic for the amazing writer Helennotoftroy. Get well soon!

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_**Thunder's Half**_

**V.**

It was not until they were halfway across the Atlantic that Tony strolled into the Helicarrier's main console room. Steve was sitting at the glass table, fiddling with a Rubik's cube. A bag of peanuts lay opened by his side.

Tony plopped into one of the rolling chairs across from Steve. "So what was that all about?" he asked.

"With Loki it's hard to say," Steve replied. "Apparently that's how he really looks." He scratched at the fresh bandage on his face.

Tony took a peanut from the bag, shelled it, and popped it into his mouth. "I'm not talking about him," he said. "I'm talking about you."

Steve almost did not meet that pointed dark stare. He sometimes forgot that for all of Stark's social awkwardness the latter was not as emotionally insensitive as he led others to believe. There was a reason Pepper Potts had worked for him for so long.

Steve set down the cube and sighed. "It's nothing," he said. "Just a little—"he broke off and sighed again. Tony waited patiently. "When I saw that much ice I was reminded of, you know."

"Hey, it's cool—no pun intended there," Tony replied, taking another peanut. "I have issues with caves and people dunking me. Aaaannd people handing me things, and chintzy bourbon and power outages and…well, actually I have issues with a lot of things, but who doesn't these days?" Steve gave something between an exhale and a chuckle.

"So how'd you get over it?" Tony asked.

"What?"

"You came back. We're big men, Cap, and we can talk about our feelings." Tony seemed to consider. "Sometimes."

Steve rolled his eyes. "Running into Loki is enough to take your mind off of anything," he began. "But even that bastard noticed. For half the trip he was informing me of the different ways ice can kill people."

Tony snorted. "Figures."

"Yeah, swell. Just as I was about to stick my shield where the sun didn't shine…well, I don't know. Something changed," Steve said, giving a lopsided smile. "All that talk of hypothermia and frozen water puncturing your cell walls kind of made me realize that there are worse things out there."

Tony wore an expression that Steve typically only witnessed when he was creating files on his 3D database. Not surprised; only inquisitive. "You think Reindeer Games did that on purpose?" Tony asked. "I hate to admit it, but his asshole meter was pretty low today. Maybe it was the new makeover."

"I don't know." Steve looked down at his cube and shook his head. "There's a lot I don't get—that I don't think any of us are really supposed to get, but I know we could use Thor back on the team," he said.

Tony pushed back his rolling chair. "Agreed," he grunted as he eased himself out of it. "C'mon, let's take your mind off it, Cap." He grinned and clapped a hand on Steve's shoulder. "What are your feelings on the Blue Man Group?"

x

The traducing _vox populi_ on Asgard claimed that the second son of Odin was inept at fighting. Quite the contrary, Loki could fight just fine. He simply preferred not to. Why sport all of those mangling scars when your head worked just as well? The few beings on Asgard who could ever provoke Loki into an actual physical match were, respectively, Sif and Thor. The rest he could send quivering with merely a wag of his tongue and nothing more.

As such, Loki could not remember being this sore since the good Doctor Banner had forcibly introduced him to a tile floor. Granted Thor's brute strength was a challenge to combat on a good day, but the energies from lost worlds made him increasingly unpredictable in battle. Although Loki himself was at the peak of his own power, he was already on battle-strategy number nine.

A fire burned in place of most of the forest—a direct result of Thor's lightning, so sharp and so hot that it had melted the surrounding snow and had set the trees ablaze. While fending off Thor with one hand Loki spent a good portion of his magic on smothering the flames. After all, fire was lethal to him now that he was wearing the skin of a Frost Giant. He hid in the smoke, but Thor spun his hammer and swept it back with a breeze. He tried calling to the animals of the earth in the Allspeak, but even they were afraid to come to his aid. All the while Thor fought fey and feral, using Mjölnir to coalesce the atmosphere and the land as one. This went on for some time.

Trees would not hold Thor. Neither would the Wind nor the Water. To some loose extent Loki could understand why Thor was fighting so hard; his brother was slowly being taken over from the inside out and was more confused and angry about that than he actually was with Loki. What Loki could not understand was why _he_ was fighting just as passionately.

After roughly a day of trying to pin Thor down Loki had had enough. Sparring had never really been his thing. Loki licked the scars around his lips. Time to bring out the big guns, as he believed they said here on Midgard.

He beckoned the liquid fire from beneath the earth, the magma of quiescent volcanoes, and cooled it to form obsidian serpents. The magic protested against his skull but Loki ignored it and _pushed;_ hundreds of snakes formed from ropy black matter, each as long as a river. They hissed and coiled around Thor, bearing fangs that dripped with the pollutions of the ground: pesticides, oil, sludge, acid.

"This might smart a little, brother," Loki said and made a gesture with his hand. The snakes sunk their fangs into Thor's flesh easier than a butter knife through cheese. When Thor's struggles weakened and slowed Loki walked over to him and placed his fingers at his brother's temples. The dark energy pulsed underneath Thor's skin, alive and tingling.

Loki faltered. He had gone through every possible scenario in his head, every possible outcome, but now that the figurative equivalent of the Big Red Button lay just beneath his fingers he still hesitated to push it. It would be so easy to simply leave Thor as he was. Why should he care if his brother fell from grace? It was what Loki had ever wanted and dreamed, after all.

And yet, there was something so unsatisfying about it. Who was Yin without his Yang?

At that moment Loki hated dichotomies with such a passion that he imagined the ground beneath him to crack with his anger. Two frustrated tears, dark blue, squeezed out and quickly escaped down the sides of his face before Loki even had the chance to register them. Curse the ancient Seid of Freya, curse the House of Odin. Curse Jötunheim. Curse Laufey for not having destroyed him at birth.

Loki took a breath and dispelled the corrupting magic.

For a moment he could feel Thor's essence, and, like he had always suspected, it was _gold._ Coruscating, molten. Like the threads the Norns spun at the base of Yggdrasil, like the Tiger's Eye amber of the great halls. Like Gungnir and Heimdall's teeth and the eyes of the fallen Kings of Valhalla. For a moment it warmed Loki and Loki found his rage momentarily forgotten. He felt, for the first time in centuries, good.

And then it was gone. The deed was done and Thor slumped to the ground with a groan. His red, red cape pooled around him, velvet mixing with blood. The igneous serpents gave a final flick of their tongues and returned to the earth.

Loki rose and stood over his brother. "Go find your little team when you can walk," he told him, though Thor was mostly lost to unconsciousness. "My work here is done." For a split second Loki's eyes flashed gold before dimming to their natural ruby red, as they had always been.

He barked something of a laugh then, splaying his fingers out before him. They were slender and blue—magician's fingers, but still his fingers right down to the bony knuckles. Loki wondered if they would prune again in Urd's Well.

Today he had saved Midgard from the weapon of his ancestors, along with freeing his brother from nefarious influences in the process. He had not done too shabbily in the end, horns and all. Loki wondered what Odin's face would look like when he discovered that he had almost turned his precious son into an agent of black magic. The image brought more exhausted laughter.

Thor would be alright. He would find his comrades and lover and proceed to stuff processed Earth food into his mouth and laugh along with them. Loki would return to Asgard. He did not expect anyone to thank him, but he preferred it that way. Loki did not believe in redemption any more than he did in love or freedom. That saccharine gold feeling of Thor's was merely fleeting, fading, being swallowed under Loki's own waves of blue and hoarfrost. It did not matter to Loki if his actions earned him a little more respect from those that he detested. He did not care if the Allfather was proud of him or not for what he had done. They were all lost to him, anyway.

Or so he told himself as Huginn swooped down and opened a portal to the place he had once called home.

_End._

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_**Author's note:** thank you all for reading! This, in all honesty, was a pain to write for numerous reasons, but I hope it turned out alright in the end. There are so many stories out there of Loki being possessed. I randomly had the idea to have _Thor_ be the one possessed for once and wanted to see what I could do with it. I always have the compulsion to re-read and tweak my stuff even after posting, but I will try to keep my, ah, post-posting edits to a minimum. This will be posted at my DW account as well (fourteenpavanes). To Helennotoftroy: I hope you like it.  
_


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